1. Field of the Invention
The present invention relates to an image recording method for recording an image by utilizing photosensitive microcapsules and, more particularly, to an image recording method utilizing photosensitive microcapsules which are rendered hardenable and which are further hardened by heating.
2. Description of the Related Art
Conventional image recording methods utilizing photosensitive microcapsules are disclosed, for example, in U.S. Pat. Nos. 2,548,366, 3,775,424, 4,399,209, 4,440,846, 4,416,966, 4,554,235, 4,576,891 and 4,587,194 and in Japanese Patent Laid-Open Nos. Sho 48-95420, 51-16807, 57-124343, 57-179836, 57-197538 and 62-174195.
These image recording methods utilize three kinds of photosensitive microcapsules each of which encapsulates therein a dye precursor, a dye or a pigment of cyan, magenta and yellow, respectively. The characteristics of each photosensitive microcapsule are as follows. Specifically, a photosensitive microcapsule encapsulating therein a precursor, a dye or a pigment of cyan is hardened upon exposure with red light having a wavelength in the vicinity of 650 nm. Similarly, a photosensitive microcapsule encapsulating therein a precursor, a dye or a pigment of magenta is hardened upon exposure with green light having a wavelength in the vicinity of 550 nm. A photosensitive microcapsule encapsulating therein a precursor, a dye or a pigment of yellow is hardened upon exposure with blue light having a wavelength in the vicinity of 450 nm.
A photosensitive recording medium and a transfer medium are used for performing image recording which utilizes such characteristics of the photosensitive microcapsules. The photosensitive recording medium comprises a substrate and a layer of three kinds of photosensitive microcapsules deposited uniformly on the substrate. The medium to be transferred comprises the substrate and a developer layer or an absorbent layer uniformly deposited thereon. When the photosensitive microcapsules encapsulate a dye precursor, a usable transfer medium has a developer deposited thereon. The developer forms color by the reaction with the dye precursor which flows out upon rupture of the photosensitive microcapsules. When the photosensitive microcapsules encapsulate a dye or a pigment, a usable transfer medium has an absorbent deposited thereon. The absorbent absorbs the dye or pigment which flows out upon rupture of the photosensitive microcapsules.
In this image recording method, red (R), green (G) and blue (B) lights corresponding to an original image are simultaneously or independently irradiated to the photosensitive microcapsule layer of the photosensitive recording medium, whereby only photosensitive microcapsules exposed with light having a predetermined wavelength are hardened. Accordingly, a chemical latent image corresponding to the original image is formed on the photosensitive microcapsule layer uniformly deposited on the substrate. Further, the photosensitive recording medium and the transfer medium are superposed with each other such that the photosensitive microcapsule layer having the chemical latent image formed thereon is opposed to the surface of the transfer medium on which the developer or absorbent is deposited. Thereafter, pressure or heat is applied to the two media for rupturing the unhardened photosensitive microcapsules. The contents encapsulated in the ruptured photosensitive microcapsules are transferred onto the transfer medium having the developer or absorbent deposited thereon, whereby an image is recorded on the transfer medium.
An image recording method disclosed in Japanese Patent Laid-Open No. 61-275242 employs photosensitive microcapsules having remarkably high sensitivity, thereby rapidly obtaining a recording image of high quality with excellent reproduction.
These image recording methods utilize three kinds of photosensitive microcapsules each of which encapsulates therein a dye precursor, a dye or a pigment of cyan, magenta and yellow, respectively. The characteristics of each photosensitive microcapsule are as follows. Specifically, a photosensitive microcapsule encapsulating therein a precursor, a dye or a pigment of cyan is rendered hardenable when exposed with red light having a wavelength in the vicinity of 650 nm, and further is hardened by heating. Similarly, a photosensitive microcapsule encapsulating therein a precursor, a dye or a pigment of magenta is rendered hardenable when exposed with green light having a wavelength in the vicinity of 550 nm, and further is hardened by heating A photosensitive microcapsule encapsulating therein a precursor, a dye or a pigment of yellow is rendered hardenable when exposed with blue light having a wavelength in the vicinity of 450 nm, and further is hardened by heating.
A photosensitive recording medium and a transfer medium are used for performing image recording which utilizes such characteristics. The photosensitive recording medium comprises a substrate and a photosensitive microcapsule layer of three kinds of photosensitive microcapsules uniformly deposited on the substrate. The transfer medium comprises a substrate and a developer layer or an absorbent layer uniformly deposited thereon. When the photosensitive microcapsules encapsulate a dye precursor, a usable transfer medium has a developer deposited thereon. The developer forms color by the reaction with the dye precursor which flows out upon rupture of the photosensitive microcapsules. When the photosensitive microcapsules encapsulate a dye or a pigment, a usable medium to be transferred has an absorbent deposited thereon. The dye or pigment is too high in permeation into paper as well as non-volatile. If the dye or pigment is transferred to a transfer medium to be transferred having no absorbent layer such as a plain sheet, the transfer medium gets wet. This absorbent absorbs the dye or pigment which flows out upon rupture of the photosensitive microcapsules.
Initially, red, green and blue lights corresponding to an original image are simultaneously or independently radiated to the photosensitive microcapsule layer of the photosensitive recording medium, thus causing stones or pits to form in the photosensitive microcapsules such that the photosensitive microcapsules irradiated with light having a predetermined wavelength are rendered hardenable. Subsequently, the hardenable photosensitive microcapsules are hardened by heating, thereby forming on the photosensitive microcapsule layer a chemical latent image corresponding to the original image. Further, the photosensitive recording medium and the transfer medium are superposed with each other such that the photosensitive microcapsule layer having the chemical latent image formed thereon is opposed to the surface of the transfer medium on which the developer or absorbent is deposited. Thereafter, pressure or heat is applied to the two media for rupturing the unhardened photosensitive microcapsules. The contents encapsulated in the ruptured photosensitive microcapsules are transferred onto the transfer medium having the developer or absorbent deposited thereon, whereby an image is recorded on the medium to be transferred.
However, the above-mentioned conventional and general image recording method using photosensitive microcapsules can record an image only on the specific transfer medium on which the developer or absorbent is deposited. In other words, the image can be recorded onto the transfer medium having the developer or absorbent deposited thereon, whereas the image recording cannot be carried out on an optional medium to be transferred such as a plain sheet.
Accordingly, there has been proposed an image recording method disclosed in Japanese Patent Laid-Open No. Sho 62-209444 in which a transfer medium having the developer deposited thereon is not required, i.e., an image can be recorded on a transfer medium such as a plain sheet. This method employs a photosensitive recording medium in which photosensitive microcapsules and a developer are deposited on a single substrate as well as a transfer medium such as a plain sheet. According to this method, however, the contents encapsulated in the photosensitive microcapsules may soak into or be repelled from the transfer medium in excess depending on a type of the transfer medium, so that an excellent recorded image cannot be obtained. Specifically, this method entails a problem such that the contents in the photosensitive microcapsules undesirably soak into the plain sheet or are repelled from, for example, an overhead projector (OHP) sheet.